A better way to remove or neutralize the pollutants found in industrial exhaust gases is needed. Among the common pollutants are organic compounds, halogenated organic compounds, carbon monoxide, nitrogen and sulfur oxides, and hydrogen. Three groups of catalysts are known to neutralize organic compound vapors.
Catalysts coated with precious metals are the first such group. Generally, platinum and palladium are used in quantities of 0.1-0.05 weight per cent on carriers such as aluminum oxide. Presently, Soviet industry produces such catalysts in limited quantities. The catalysts of this group are the subject of USSR Certificate of Authorship No. 592,436 naming O. P. Baburova, T. A. Kruzhkova, et al. as authors.
Group 2 of such catalysts includes bulk oxides of copper, chromium, manganese, etc. (A bulk material as identified in this document is a homogeneous material, as opposed to a material supported on a substrate or support made of a different material.)
A typical catalyst of this group is described in U.S.S.R. Patent No. 433,665, issued to Franco Buonomo, Vittorio Fattore, Janfranco Zanoni, and Bruno Notari as the inventors. The catalyst of that patent consists of a mixture of oxides of copper, manganese, nickel, cobalt, and chromium. The patent states that this catalyst is useful to purify combustion engine exhausts which contain carbon monoxide and hydrocarbons, specifically butane (C.sub.4 H.sub.10).
A similar catalyst was proposed by L. D. Kudryavtseva, I. F. Sotnikov, et al. in USSR Certificate of Authorship No. 326977. This catalyst contains manganese, copper, magnesium, calcium and titanium. This catalyst is stated to purify gaseous exhausts by treating butadiene-1,4, halogenated organic compounds, toluene, etc.
The third group of such catalysts includes oxides of copper, chromium, manganese, etc. which are coated on such carriers as aluminum oxide. The catalysts of this group are the least expensive ones.
Each of these prior catalysts has disadvantages. Catalysts of the first group which contain precious metals are expensive and ineffective for removing organic compound aerosols from exhausts.
Catalysts of the second and third groups, which do not contain precious metals, operate at higher temperatures and consume more heat. These catalysts are poisoned by halogens (for example, chlorine), so they are ineffective for purifying gaseous exhausts containing hydrogen halides or halogenated organic compounds.
Existing catalysts accumulate aerosols of resinous and other organic compounds on their surfaces when used for neutralization of gaseous exhausts containing such aerosols. As a result, oxidation occurs irregularly and is accompanied by strong exothermic effects which lead to the overheating of the catalyst to a temperature as high as 1,000.degree. C. Existing catalysts lose their catalytic properties due to irreversible changes in their structure at some temperature between about 450.degree. and 900.degree. C.
Accordingly, one object of the present invention is to provide a catalyst which is useful for neutralization of gaseous exhausts which contain vapors and aerosols of organic and halogenated organic compounds, as well as some oxygen.
An additional object of the invention is to improve the activity of catalysts for oxidizing carbonaceous and other pollutants in exhaust streams.
Another object of the invention is to improve the thermal resistance of catalysts for oxidizing carbonaceous and other pollutants in exhaust streams.
A different object of the invention is to improve the resistance of such catalysts to poisoning by compounds of chlorine or other halogens, sulfur, or nitrogen.
An additional object of the invention is to improve the resistance of catalysts for oxidizing carbonaceous and other pollutants in exhaust streams to deactivation by aerosols of resins and other organic compounds.
Another object of the invention is a catalyst adapted for treating the exhausts of factories which produce and process electrodes for metallurgy.
Still another object of the invention is a catalyst adapted for treating the exhausts of factories which produce and process chemical fibers.
Yet another object of the invention is a catalyst adapted for treating the exhausts of factories which produce and process man-made leather and other plastics.
Yet another object of the invention is a catalyst adapted for treating the exhausts of factories which produce and process varnish or paint.
Another object of the invention is to provide an improved method for treating such exhausts by contacting the exhausts with an improved catalyst.
One or more of these objects, as well as other objects which will become evident to one of ordinary skill in the art who is familiar with the present invention, are contemplated by the present inventors.